Harmonic frequencies of fundamental power system waveforms have recently become a concern to electric power utilities. Harmonics on the power lines cause excessive losses in induction and synchronous machines and tend to create over-voltages and excessive currents as a result of resonance to harmonic voltages and currents on the network. In addition, harmonics tend to cause capacitor bank failure from dielectric breakdown or reactive power overload, and interfere with microprocessor control systems and other circuitry synchronized to the power lines.
Harmonics are created in power distribution networks by non-linear loads resulting from new technologies such as silicon-controlled rectifiers, power transistors and microprocessor controls which create load-generated harmonics throughout the network. Furthermore, power devices and equipment now are more critically designed and, when iron-core devices are involved, tend to operate more into their inherently non-linear regions.
Utilities thus now are beginning to set standards limiting injection of harmonics into power distribution networks. To intelligently select a standard and effectively enforce it, however, the harmonic content of existing networks must be characterized. There accordingly exists a need to monitor the harmonic content of power distribution networks, to enable standards to be established, and to determine the locations of harmonic sources so that corrective action, if appropriate, can be taken.
One object of the invention, therefore, is to provide a method of and system for monitoring harmonics in power distribution networks.
Another object is to provide a method of and system for identifying the magnitudes and phase angles of power harmonics on electrical power distribution networks.
A further object is to provide a method of and system for determining the locations of power harmonic sources relative to reference nodes within power distribution networks.
A further object is to provide line monitoring apparatus for the above purposes that accumulate and analyze harmonic component data automatically to generate summary reports.